In short, we have to realise the danger of careless driving, in order to avoid or at least to reduce the high rate of car accidents.

careless 是由 care（小心、谨慎）加上否定后缀 -less（表示“没有”）组成的形容词，字面意思是“不小心的”，即“粗心的、疏忽的”。